The invention herein relates to jacketing for insulated pipe fittings, particularly elbows. In the past it has been common to insulate straight runs of pipe and to cover the insulation with protective jacketing, either of plastic or metal. Where straight runs of pipe have been involved, fabrication and installation of the insulation and jacketing has been easy, since the insulating can be fabricated in semi-cylindrical segments and the jacketing applied in sheet form either before or after installation of the insulation.
The numerous fittings in a pipe line have, however, created considerable difficulty in fabrication and installation of equivalent insulated coverings. Resort has generally been had to custom fabricated insulated coverings (such as those shown in U.S. Pat. Nos. 3,153,546, and 3,631,898) or mitered sectional fittings (such as those shown in U.S. Pat. No. 3,222,777) or to the use of troweled and molded cements covered with fabric strips such as burlap.
The insulation and jacketing of the most common type of pipe fittings, 90.degree. elbows, was vastly simplified by the introduction several years ago of a one piece foldable elbow cover of the type shown in U.S. Pat. No. 3,495,629, issued to Botsolas et al. Because of its significant superiority and ease of use, the Botsolas et al elbow cover rapidly gained wide acceptance in the market place, a distinction it enjoys to this day.
Recently there has been a recognition that, despite the Botsolas et al fitting cover's superiority over other types of elbow jacketing, it has one disadvantage. This disadvantage lies in the Botsolas et al fitting cover's inability to maintain itself in a position intermediate its initial open shape and the final elbow shape. It therefore cannot be self-retained in a preliminary position covering the insulated elbow, but rather must be mechanically held in its final shape by the installer prior to final securing (with tape, pins, or the like), since its resilience otherwise causes it to open up and resume its original trough-like shape. In some circumstances such as where the installation is being made in a cramped location the installer may therefore have difficulty retaining the cover in its closed elbow position while he applies the tape or other securing means.
One approach to overcoming the tendency of the Botsolas et al cover to spring open has been to fold the cover into a semi-closed position immediately following fabrication and then to heat treat the folded cover in an oven for a few minutes which causes the cover to lose the tendency to reopen spontaneously. This approach, however, has been unsatisfactory for two reasons: it requires an extra manufacturing step with the attendant time and expense and also it has been found that if the heat treated cover is reheated later (as by being stored in a hot warehouse for a prolonged period) the effect of the heat treating is destroyed and the cover once again regains its tendency to reopen.
Consequently it would be of major significance to have a fitting cover which would incorporate all of the advantages of the Botsolas et al cover but which would have incorporated into its structure and geometry means which would allow it to be retained in a convenient intermediate partially folded position for installation without the need of mechanical restraints.